Ceramic materials have long been recognized as superior materials for applications where attributes such as hardness and stiffness, strength and oxidation resistance at elevated temperatures, high thermal conductivity, low coefficient of thermal expansion, and resistance to wear and abrasion are of primary value. Structural applications of conventional monolithic ceramics have generally been limited due to the materials' brittle nature and low toughness. Such characteristics are markedly improved by reinforcement of the monolithic ceramics, e.g., by creating tougher fiber reinforced ceramics. Thus, fiber reinforced ceramic matrix composite (CMC) systems are of major interest to the high-temperature user community including the aerospace industry.
In one common form, carbon fibers are embedded in a silicon carbide matrix to create a carbon/silicon carbide composite system commonly referred to as C/SiC (typical nomenclature references the reinforcement first followed by the matrix). In order for a CMC system, such as C/SiC, to provide the requisite toughness, a fiber/matrix interface is typically required. This interface provides a weak bond between the fibers and the matrix and allows limited frictional fiber slippage, which provides toughness, and a crack deflection path around, rather than through, the fiber, further enhancing the toughness.
Typically, C/SiC composites have their interface and matrix created with a costly chemical vapor deposition (CVD) process. This process involves CVD reactors, which are complex chemical reactors that are expensive to build, maintain and operate. CVD reactors also tend to be specific to the application for which they were originally built; and, as applications have increased in size, large C/SiC parts have been built by fabricating and joining smaller sub-sections into the larger part. Furthermore, processing time in a CVD reactor to produce parts having acceptable structural thickness and density is usually lengthy. Also, the cost of running a CVD reactor tends to be significantly higher than the cost of running conventional furnaces, such as inert atmosphere furnaces. Accordingly, the use of CVD reactors has hindered the acceptance of large C/SiC structures due to the lengthy processing times and high costs.
As a result, there is a need for an efficient process for fabricating CMC (e.g., C/SiC) structures with shorter processing time, lower cost, and enhanced scale-up capabilities, and which produces parts with sufficient strength to withstand high loads and temperatures particularly, but not solely, in environments, such as combustion environments that are oxidizing relative to both the carbon reinforcement fibers and the non-oxide matrix.